Electronic system and method for testing capacitive circuit lines

ABSTRACT

The invention relates to an electronic system comprising a plurality of circuit lines and an error detection component for detecting errors on and between the plurality of circuit lines, wherein each circuit line having a voltage different to ground level, the error detection component being adapted to perform a test routine comprising the steps of: —selecting one circuit line out of the plurality of circuit lines; —determining the voltage of the selected circuit line and storing the voltage value; —discharging the selected circuit line to ground level; —iteratively repeating the aforementioned steps of selecting a circuit line, determining and storing its voltage and discharging for further circuit lines; —comparing the stored voltage values associated with the respective circuit lines with a threshold value; and —generating an error indicator if at least one stored voltage value is below the threshold value.

The present invention relates generally to the field of error detection.More specifically, the present invention is related to an electronicsystem and a method for testing circuit lines, specifically in householdappliances.

BACKGROUND OF THE INVENTION

Electronic systems used in home appliance industry require compliancy ofsafety relevant norms, specifically norms related to safety-relevantsignal handling (e.g. IEC/UL/CSA 60730).

Said electronic systems may comprise analog multiplexers in order toperform a time-dependent multiplex of a plurality of signals to acertain input of an electronic component, e.g. a microcontroller.Thereby, a plurality of signals can be connected to the electroniccomponent which may provide a limited number of input ports.

In order to comply with the requirements of safety relevant norms, acommon solution is to dedicate an input of each multiplexer used in theelectronic system to a fixed reference signal. The reference signal maybe a reference voltage having a preassigned value. By regularly samplingsaid reference signal the correct function of the electronic system canbe tested.

A drawback of said common solution is that one input per eachmultiplexer is reserved for error detection. Thus, the number ofavailable inputs is reduced and in certain configurations, furthermultiplexers are needed because of the reduced number of availablemultiplexer inputs.

Accordingly, there is a need for improvements of existing errordetection methods in electronic systems in order to improve theutilization of the available hardware resources.

SUMMARY OF THE INVENTION

It is an objective of embodiments of the invention to provide for anelectronic system with error detection and a method for detecting errorsin electronic systems which show improved utilization of the availablehardware resources. The objective is solved by the features of theindependent claims. Preferred embodiments are given in the dependentclaims. If not explicitly indicated otherwise, embodiments of theinvention can be freely combined with each other.

According to a first aspect of the invention, the invention relates toan electronic system comprising a plurality of circuit lines and anerror detection component for detecting errors on and between theplurality of circuit lines, wherein each circuit line having a voltagedifferent to ground level, the error detection component being adaptedto perform a test routine comprising the steps of:

-   -   selecting one circuit line out of the plurality of circuit        lines;    -   determining the voltage of the selected circuit line and storing        the voltage value;    -   discharging the selected circuit line to ground level;    -   iteratively repeating the aforementioned steps of selecting a        circuit line, determining and storing its voltage and        discharging for further circuit lines;    -   comparing the stored voltage values associated with the        respective circuit lines with a threshold value; and    -   returning an error indicator if at least one stored voltage        value is below the threshold value.

Specifically, the steps of comparing the stored voltage values with athreshold value and discharging the selected circuit line to groundlevel may at least partially overlap, i.e. may be at least partiallyperformed simultaneously.

By performing the aforementioned test routine, it is possible todetermine errors correlated with circuit lines without reserving a pinof the multiplexer for error detection. In addition it is possible todetect not only errors or faults on a certain circuit line but alsobetween two circuit lines, e.g. neighbored circuit lines.

According to further embodiments, the circuit lines are lines comprisingthe inputs/outputs or a common output/input of a bidirectionalmultiplexer and the error detection component is adapted to select onecertain circuit line by addressing the control inputs of thebidirectional multiplexer. Preferably, the bidirectional multiplexercomprises one common output/input line and a plurality of input/outputlines to be connected to the common output/input line independently fromeach other by addressing control inputs of the bidirectionalmultiplexer. The common output/input line may be coupled with the errordetection component. The error detection component may be implemented ina microcontroller. By a controlled addressing of the multiplexer, aplurality of different circuit lines may be analyzed.

According to further embodiments, the error detection component isadapted to perform an analog to digital conversion of the determinedvoltage value. Thereby it is possible to determine the voltage of thecircuit line in the digital domain. In addition, the voltage value maybe stored for further investigation in a memory provided by or connectedwith the error detection component.

According to further embodiments, the error detection component isadapted to discharge the selected circuit line by means of a pull-downtransistor. Preferably, the error detection component is implemented bya microcontroller, wherein the discharging of the selected circuit lineis performed by setting the pin of the microcontroller to digital lowlevel. Thereby, the discharging of the circuit line can be obtained byswitching the pin or port of the microcontroller connected to thecircuit line to be analyzed to low level.

According to further embodiments, the error detection component isadapted to perform a value range check for determining if the voltage ofthe circuit line lies within a predetermined range. By using the valuerange check, for example, it is possible to determine if the voltagevalue of the selected circuit line is short-circuited to positive supplyvoltage.

According to further embodiments, the error detection component isadapted to perform the aforementioned test routine iteratively at leasttwo times. Thereby it is possible to detect floating circuit lines withundefined potential, avoiding that floating circuit lines whichcoincidentally have a voltage value above the threshold value are deemederrorless.

According to a further aspect, the invention refers to a method fordetecting errors on and between a plurality of circuit lines having avoltage different to ground level, the method comprising the followingsteps:

-   -   selecting one circuit line out of the plurality of circuit        lines;    -   determining the voltage of the selected circuit line and storing        the voltage value;    -   discharging the selected circuit line to ground level;    -   iteratively repeating the aforementioned steps of selecting a        circuit line, determining and storing its voltage and        discharging for further circuit lines;    -   comparing the stored voltage values associated with the        respective circuit lines with a threshold value; and    -   returning an error indicator if at least one stored voltage        value is below the threshold value.

According to a third aspect, the invention refers to a computer-readablestorage medium comprising instructions that, when executed by at leastone processor of an appliance, cause the appliance to perform anoperation for detecting errors on and between a plurality of circuitlines having a voltage different to ground level, the operationcomprising the following steps:

-   -   selecting one circuit line out of the plurality of circuit        lines;    -   determining the voltage of the selected circuit line and storing        the voltage value;    -   discharging the selected circuit line to ground level;    -   iteratively repeating the aforementioned steps of selecting a        circuit line, determining and storing its voltage and        discharging for further circuit lines;    -   comparing the stored voltage values associated with the        respective circuit lines with a threshold value; and    -   generating an error indicator if at least one stored voltage        value is below the threshold value.

The term “essentially” or “approximately” as used in the invention meansdeviations from the exact value by +/−10%, preferably by +/−5% and/ordeviations in the form of changes that are insignificant for thefunction.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the invention, including its particular featuresand advantages, will be readily understood from the following detaileddescription and the accompanying drawings, in which:

FIG. 1 shows an example schematic illustration of an electronic systemaccording to the present invention;

FIG. 2 shows an example schematic illustration of a multiplexerimplemented in the electronic system according to FIG. 1; and

FIG. 3 shows an example flow chart of an embodiment of a test routine.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described more fully with reference tothe accompanying drawings, in which example embodiments are shown.However, this invention should not be construed as limited to theembodiments set forth herein. Throughout the following descriptionsimilar reference numerals have been used to denote similar elements,parts, items or features, when applicable.

FIG. 1 illustrates an embodiment of an electronic system 1. Theelectronic system 1 comprises a capacitive-type value generatingcomponent 2. The value generating component 2 may be any capacitive-typecomponent which is adapted to provide measureable values, specificallyelectrical values. For example, the value generating component 2 may bea capacitive-type touch pad comprising a plurality of touch buttons,wherein the touch pad may provide a voltage value correlated to therespective touch button dependent on the touching status (touched ornot). According to a further example, the value generating component 2may be a temperature regulating and limiting control comprising multipleanalog temperature sensors (e.g. NTC-type), wherein the voltage droppedover the temperature sensor is indicative for the temperature of thetemperature sensor.

The value generating component 2 may be connected to a microcontroller 3comprising a set of pins 3.1. Said pins 3.1 may be preferably analoginputs and digital outputs wherein the functionality of the pins dependson a control signal applied to the microcontroller 3. For analyzing theelectrical values provided by the value generating component 2, eachoutput 2.1 of the value generating component 2 has to be connected to apin 3.1 of the microcontroller 3 to analyze the electrical valueprovided by the value generating component 2.

In case that the number of pins 3.1 of the microcontroller 3 is lowerthan the number of outputs 2.1 provided by the value generatingcomponent 2, a multiplexer 4 is used for multiplexing multiple outputs2.1 to one pin 3.1 of the microcontroller 3.

FIG. 2 shows an example embodiment of a multiplexer 4 to be used in anelectronic system 1. The shown multiplexer 4 may be an 8-to-1multiplexer which is adapted to switch the electrical signal provided atone of the eight inputs 4.1 to a common output 4.2 based on a controlsignal provided to the multiplexer 4. So, at a certain point of time, acertain input 4.1 is connected to the output 4.2 of the multiplexer 4allowing a time-dependent analysis of the electrical value provided bythe value generating component 2 by means of the microcontroller 3.

The multiplexer 4 may be a bidirectional multiplexer, i.e. themultiplexer 4 may be also be operated in the inverse direction, whereinthe common output 4.2 serves as input and the multiple inputs 4.1 servesas outputs 4.2. Hence, the inputs 4.1 may be also referred to asinputs/outputs 4.1 and the common output 4.2 may be also referred to ascommon output/input 4.2.

The multiplexer 4 may further comprise a set of control inputs 4.3enabling an addressing of the multiplexer such that a certaininput/output 4.1 is electrically connected to the common output/input4.2. Thereby a controlled switching according to a scheduling ispossible. The multiplexer 4 may further comprise an inhibit input 4.4 tosimultaneously disable the switches of the multiplexer 4 when ahigh-level (e.g. 5V) is applied to the inhibit input 4.4.

In order to comply with the aforementioned safety relevant norms ofelectronic systems used in the home appliance industry (IEC/UL/CSA60730), error detection is required.

Said error detection may be adapted for detecting:

-   -   short circuits of the circuit lines 6, 7 connected to the        multiplexer 4 to ground, i.e. zero potential;    -   short circuits of the circuit lines 6, 7 connected to the        multiplexer 4 to positive supply voltage (+Vcc) or to negative        supply voltage (−Vcc);    -   short circuits to neighboring circuit lines or pins;    -   open circuits leading to a floating potential;    -   wrong addressing of the multiplexer due to errors at the control        inputs or circuit lines connected to the control inputs.

For detecting the aforementioned errors, a test routine comprisingconsecutive steps is performed. The test routine may be implemented inan error detection component 8. Said error detection component 8 may beintegrated in the microcontroller 3. According to a further embodiment,the error detection component 8 may be implemented as a self-containedcomponent independent from the microcontroller 3. Furthermore, the errordetection component 8 may be implemented at least partially in software.

For performing the test routine for error detection, the followingrequirements may be fulfilled:

-   -   The voltage of the circuit lines 6, 7 before starting the test        routine is different to 0V, i.e. different to ground or zero        potential. The circuit lines 6, 7 connected to the value        generating component 2 may be charged at a voltage, e.g. a        voltage of 3.0V-4.0V, specifically 3.7V, because the        capacity-type value generating component 2 is working at said        voltage in normal operation.    -   The circuit lines 6, 7 and the value generating component 2 can        be electrically discharged to 0V, i.e. ground or zero potential.        Said discharging may be performed by means of a pull-down        transistor connected to ground;    -   after discharging to 0V, the voltage of the circuit lines 6, 7        stay at 0V or essentially 0V.

In the following, the test routine is described based on the flowdiagram shown in FIG. 3. The test routine may be performed by the errordetection component 8 which is preferably integrated in themicrocontroller 3. After starting the test routine, in a first step, acircuit line 6, 7 is selected (S10). In case that a circuit line 6comprising one of the plurality of inputs/outputs 4.1 should be tested,the control inputs 4.3 are driven such, that the chosen input/output 4.1is connected to the common output 4.2 of the multiplexer 4. Themicrocontroller 3 may be controlled such that the pin 3.1 of themicrocontroller 3 connected to the common output 4.2 of the multiplexer4 is set as analog input, i.e. the signal provided at the pin 3.1 isanalyzed.

Subsequently, the voltage of the selected circuit line is determined(S11). Said determination may be performed by measuring means of themicrocontroller 3. Preferably, the analog signal provided at the pin 3.1is converted from the analog into the digital domain by means of ananalog-to-digital converter (A/D-converter). Following up, the digitalvoltage value is stored (S12).

In the following step, the selected circuit line is discharged to groundlevel (0V) (S13). Said discharging may be performed by means of themicrocontroller 3. Specifically, the pin 3.1 may be set to low level bycontrolling the microcontroller 3 in the appropriate way. Thereby, thecapacitor correlated with the selected circuit line is discharged.Preferably, a pull-down transistor may be used for discharging thecircuit line. The period of time needed for discharging depends on theR-C time constant, so discharging of the circuit line takes a certainperiod of time (e.g. 1 ms-100 ms).

Following up in the test routine, there is a check whether any furthercircuit lines have to be tested (S14). If so, the test routine startsagain at step S10, i.e. a further circuit line to be tested is selected.Otherwise, if there are no further circuit lines to be tested, the atleast one stored voltage value is analyzed (S15). If at least one of thestored voltage values is below a certain threshold value (e.g. <0.1V)(S16), an error flag is generated (S17) indicating a failure within thetested electronic system 1 because a correctly configured and fullyworking electronic system 1 should give back only values above thepredefined threshold value.

In addition, a value range test may be performed. By means of the valuerange test it is possible to detect untypical deviations from typicalmeasurement values. Specifically, it is possible to detect anovershooting or undershooting of typical measurement values. Forperforming the value range test, the voltage values of the respectivecircuit lines may be checked by analog-to-digital conversion andanalyzing the digital voltage values, if the voltage values are in thedesired range.

In the following, different error scenarios which may be detected by theaforementioned test routine are described in closer detail.

Based on the test routine, an error in a circuit line comprising one ofthe control input pins 4.3 may be detected. In general, a error in acircuit line comprising one of the control input pins 4.3 may lead to awrong addressing. Due to wrong addressing, a circuit line may beselected and analyzed twice, i.e. an already tested and thereforedischarged circuit line may be tested again. Thus, during the furthertest routine, a voltage level below the threshold value may be detected.Thus, an error flag may be generated indicating an error in therespective circuit line.

Also short circuits of the circuit lines containing the inputs/outputs4.1 of the multiplexer 4 to ground may lead to a detected voltage belowthe threshold value and therefore lead to a generation of an error flag.In addition, also short circuits of inputs/outputs 4.1 to neighboringpins of the multiplexer may be detected because discharging of one ofthe short-circuited lines may lead also to a discharge of the furthercircuit line. When determining the voltage of said further circuit line,a voltage below the threshold value is detected leading to a generationof an error flag.

Even open circuit lines, e.g. broken circuit lines, may be detected bymeans of the upper-mentioned test routine. An open circuit line may befloating, i.e. the voltage value may be not defined. Therefore, a valuerange check may not reliably detect an error when analyzing a floatingpin. By performing said test routine, the floating circuit line may beconnected with the discharged input of the A/D-converter leading to adischarging of the floating circuit line. Therefore, in order to detectall floating circuit lines it is possible to perform the test routinetwice. Preferably, the test routine is performed in different directionsand/or different order. Preferably the test routine is performedregularly, namely in a first step in a forward direction and in a secondstep in a backward direction wherein between both steps normal operationis performed in order to ensure that the circuit lines 6, 7 comprise thenormal operation voltage.

Similarly, also errors regarding the circuit lines comprising themultiplexer output 4.2 or the inhibit input 4.4 may be detected.

Above, embodiments of the electronic system according to the presentinvention as defined in the appended claims have been described. Theseshould be seen as merely non-limiting examples. As understood by askilled person, many modifications and alternative embodiments arepossible within the scope of the invention.

LIST OF REFERENCE NUMERALS

1 electronic system 2 value generating component 2.1 output 3microcontroller 3.1 pin 4 multiplexer 4.1 input 4.2 output 4.3 controlinput 4.4 inhibit input 5 control input 6 circuit line 7 circuit line 8error detection component

1. Electronic system comprising a plurality of circuit lines and anerror detection component for detecting errors on and between theplurality of circuit lines, wherein each circuit line has a voltagedifferent from ground level, the error detection component being adaptedto perform a test routine comprising the steps of: selecting one circuitline out of the plurality of circuit lines; determining the voltage ofthe selected circuit line and storing the voltage value; discharging theselected circuit line to ground level; iteratively repeating theaforementioned steps of selecting a circuit line, determining andstoring its voltage and discharging for further ones of the circuitlines; comparing the stored voltage values associated with therespective circuit lines with a threshold value; and generating an errorindicator if at least one stored voltage value is below the thresholdvalue.
 2. Electronic system according to claim 1, wherein the circuitlines are lines comprising the inputs/outputs or a common output/inputof a bidirectional multiplexer and the error detection component isadapted to select one certain circuit line by addressing the controlinputs of the bidirectional multiplexer.
 3. Electronic system accordingto claim 1, wherein the error detection component is adapted to performan analog to digital conversion of the determined voltage value. 4.Electronic system according to claim 1, wherein the error detectioncomponent is adapted to discharge the selected circuit line by means ofa pull-down transistor.
 5. Electronic system according to claim 1,wherein the error detection component is implemented by amicrocontroller, wherein the discharge of the selected circuit line isperformed by setting a pin of the microcontroller to digital low level.6. Electronic system according to claim 1, wherein the error detectioncomponent is adapted to perform a value range check for determining ifthe voltage of the selected circuit line lies within a predeterminedrange.
 7. Electronic system according to claim 6, wherein the errordetection component is adapted to perform the test routine iterativelyat least two times in order to detect floating circuit lines. 8.Electronic system according to claim 1, wherein the steps of comparingthe stored voltage values with a threshold value and discharging theselected circuit line to ground level are at least partially performedsimultaneously.
 9. Domestic appliance comprising an electronic systemaccording to claim
 1. 10. Method for detecting errors on and between aplurality of circuit lines having a voltage different from ground level,the method comprising the following steps: selecting one circuit lineout of the plurality of circuit lines; determining the voltage of theselected circuit line and storing the voltage value; discharging theselected circuit line to ground level; iteratively repeating theaforementioned steps of selecting a circuit line, determining andstoring its voltage and discharging for further ones of the circuitlines; comparing the stored voltage values associated with therespective circuit lines with a threshold value; and returning an errorindicator if at least one stored voltage value is below the thresholdvalue.
 11. A computer-readable storage medium comprising instructionsthat, when executed by at least one processor of an appliance, cause theappliance to perform an operation for detecting errors on and between aplurality of circuit lines having a voltage different from ground level,the operation comprising the following steps: selecting one circuit lineout of the plurality of circuit lines; determining the voltage of theselected circuit line and storing the voltage value; discharging theselected circuit line to ground level; iteratively repeating theaforementioned steps of selecting a circuit line, determining andstoring its voltage and discharging for further ones of the circuitlines; comparing the stored voltage values associated with therespective circuit lines with a threshold value; and generating an errorindicator if at least one stored voltage value is below the thresholdvalue.